1. Field of the Invention
The present invention relates generally to a horizontal bandsaw machine in which a cutting head assembly carrying a bandsaw blade is lowered during a cutting operation in order to feed the blade into an underlying material, and more particularly pertains to a feed control for controlling the movement of the cutting head assembly during a cutting operation.
2. Description of the Prior Art
Conventionally, a horizontal bandsaw machine is provided with a cutting head assembly carrying a bandsaw blade. The cutting head assembly is lowered toward the material during the cutting operation so as to feed the bandsaw blade into the material. The bandsaw blade is endless and is trained around two wheels in the cutting head assembly, one of the wheels being driven. The cutting head assembly is usually raised by some known means, for example a piston-cylinder unit, and is lowered by gravity as hydraulic fluid is discharged from the cylinder.
In such horizontal bandsaw machines, the feeding force acting on the blade has to be great enough to cut hard and tough "difficult" materials. Insufficient feeding force will cause the bandsaw blade to slide over the difficult materials, without actually cutting, and as a result the blade will not only be worn uselessly, but also it will produce an undesirable work hardening of the material. For this reason, the cutting head assembly is usually so designed as to be heavy enough to exert the force required on the cutting blade to cut difficult materials.
Also, for economical and efficient cutting operations with horizontal bandsaw machines, it is of course desirable to run the blade at the highest speeds possible. Accordingly, the bandsaw blade is driven at a higher speed when cutting "normal" easy-to-cut materials which are generally soft and brittle. However, excessive speed of the bandsaw blade in cutting difficult materials will cause the bandsaw blade to simply slide over the material again with the result that the blade is worn uselessly while the material undergoes undesirable work hardening.
One of the most serious disadvantages of horizontal bandsaw machines has been that the feeding force needed to cut the difficult materials is too great to economically and efficiently cut normal materials. Excessive feeding force will force the bandsaw blade to cut into the normal materials too rapidly which in turn will produce excessive blade wear.
For the above reasons, it is on one hand desirable when cutting normal materials to run the bandsaw blade at a higher speed and to feed the same into the material so that the cutting action may be performed always at a certain optimum cutting rate which is defined as square millimeters of cut per unit of time. On the other hand, however, it is desirable when cutting difficult materials to feed the bandsaw blade into the material with a greater feeding force and at a lower operating speed. Accordingly, it is also desired in horizontal bandsaw machines to steplessly or gradually control the feeding of the bandsaw blade with an optimum travelling speed thereof according to the materials to be cut.